The present invention concerns a method and device for processing photostimulable image plate as whereby an image plate is taken out of a cassette, processed and then placed back in the same cassette while the cassette is transported from an input station to an output station
Photostimulable phosphor-coated film is increasingly employed instead of conventional film to produce x-rays for medical diagnoses. One advantage of a phosphor-coated film as a graphic reference material is its almost linear reproduction characteristic. This means that the gray scale or scale of densities of the image carrier matches the dose of radiation beamed onto it. Images obtained with photostimulable image plates are accordingly much less sensitive to excess or insufficient radiation. Another advantage of photostimulable image plates or phosphor-coated film is that they can be used over and over. Once the plate or film has been developed and the image interpreted and stored electronically, it can be erased and re-exposed.
Still another advantage of a phosphor-coated film is that it can be handled extensively like conventional x-ray film, and much existing processing equipment (e.g. cassettes, film loading-and-unloading mechanisms, etc.) can be used.
A method of and a device for handling photostimulatable phosphor-coated film is known, for example, from the European Patent No. 307,760 B1. The film is loaded into a cassette, such identifying information as patient""s name and date of birth, physician""s name, etc. is entered in a semiconductor memory on the cassette, and the film is exposed, leaving a latent image. To develop the image, the cassette is inserted into a digital reader, wherein it is opened and the film extracted and swept with radiation to stimulate it. The light emitted by the film is collected by a light collector and converted into a grid of pixels, restoring the image. The pixels can also be transmitted to a digital image processor for further treatment handling as desired.
There is a drawback to this approach. The footprint of the equipment employed to read out the film is relatively large in that the film is inserted into it from one direction, extracted from the cassette therein, and extracted in essentially the same direction for photoelectric scanning. Because of the many items of electronic equipment employed in hospitals, floor space in hospitals is at a premium.
Devices for processing photostimulable phosphor-coated film that occupy less area are known from the German Patent No. 3,733,191 C2 and the U.S. Pat. No. 5,493,128. In these devices the cassettes are forwarded vertically during processing. They are inserted into the device in one direction, displaced thereto, unloaded, and ejected in another direction. The cassettes, finished or in process, are coordinated in specific positions, especially in accordance with the U.S. Pat. No. 5,493,128, in relative complicated sorting mechanisms.
The principal object of the present invention is, accordingly, a method of and a device for processing photostimulable phosphor-coated image plates or film that will be as simple as possible and that will occupy as little area as possible.
This object, as well as other objects which will become apparent from the discussion that follows, are achieved, in accordance with the present invention, by a method whereby the cassette is rotated about a vertical axis after the image plate is extracted from it and before the image plate is returned to it. The invention also provides a device having an extraction station with an extraction mechanism for extracting the image plate from the cassette and thereafter returning the image plate to it. This extraction station rotates about a vertical axis after the plate is extracted from the cassette and before the plate is returned thereto.
In accordance with the present invention, the loaded cassette is rotated around a vertical axis while being forwarded. The cassette is opened in one position and the plate or film extracted and transported to the photoelectric scanner. While the plate or film is being scanned, the cassette, advantageously still open, is rotated farther to accept the scanned plate or film. The cassette is forwarded in a horizontal position in this embodiment. In another advantageous embodiment, however, the cassette can be forwarded essentially upright, resting on edge and tilted less than 45xc2x0 to the vertical. This approach saves a lot of space inside the processor. A processor in accordance with this embodiment can also handle two cassettes at once, one ready to be unloaded and the other to be loaded. Such a device can process considerably more plates or film at a time than can be processed at the state of the art.
In one advantageous embodiment of the present invention, the cassette is forwarded to the film-extraction location in one direction horizontally and opened, and the plate or film extracted from it. The cassette is then rotated 180xc2x0 around a vertical axis into a film-insertion position, where the photoelectrically scanned plate or film is returned to the cassette and the cassette closed. The cassette is then finally forwarded in opposition to the original direction to the delivery location, where it can be picked up at any time.
Both the cassette-insertion location (input station) and the cassette-delivery location (output station) can constitute temporary-storage locations, each accommodating several cassettes. The insertion end of the device can accordingly be continuously exploited and the cassettes picked up at the other end as time permits without impeding the operation of the device as a whole.
One particular advantage is that the whole device can be operated from one side, both of the directions traveled by the cassettes paralleling the controls.
Several locations can be included at both ends, where the cassettes can be sorted as they are inserted and ejected.
For a full understanding of the present invention, reference should now be made to the following detailed description of the preferred embodiments of the invention as illustrated in the accompanying drawings.